Bumps {rmarkdown} minimal version (#154)

# Pull Request

Part of insightsengineering/coredev-tasks#546

Necessary bump to overcome a lack of binary on ppm snapshots that causes
an error on minimum strategies for `scheduled` workflows.

DESCRIPTION

@@ -30,7 +30,7 @@ Imports:
     yaml (>= 2.1.15)
 Suggests:
     knitr (>= 1.42),
-    rmarkdown (>= 2.19),
+    rmarkdown (>= 2.23),
     testthat (>= 3.0.4),
     withr (>= 2.1.0)
 VignetteBuilder: